In a traditional manufacturing process, the completion of a product must undergo many processes, and the connection in the middle of each process often must rely on storage, transportation and other processes. Taking for example the production process of a screw and nut industry, a semi-finished product outputted from the production machine is usually placed in a carrying box. After a predetermined quantity is accumulated, it is transported by a transport unit to a predetermined location for stacking. Then, an operator will take them out for processing or inspection, sort them out according to their type, and put them into several different categories of carrying boxes. Finally, the carrying boxes loaded with the materials are stacked.
The weight of each carrying box loaded with the materials may reach several hundreds of kilograms depending on the type of material it carries, so that a stacking machine must be used for its transport operation. To prevent rocking due to, for example, improper operation, earthquake or accidental bumping or collision, which can cause the carrying boxes to topple and create a safety hazard, the height of stacking the carrying boxes is limited. Further, the stacking height of the carrying boxes is also restricted by the operating height of the stacking machine. If the stacking machine is stacked high with heavy products, such as screws, nuts, etc., the center of gravity after stacking is also high. The higher the gravity, the more it is likely to topple easily. Because the stacking height of the carrying boxes is restricted, the carrying boxes will occupy a substantial space in the factory or warehouse. Further, during storage of the materials, they are usually placed in a scattering manner, so that it is difficult to sort them out according to their respective types.
In order to solve the above problems, fixed-type material racks for placement of the materials are employed. The fixed-type material racks can facilitate sorting of the materials, and can permit the carrying boxes to stack in a high place so as to make an efficient use of the storage space. However, the fixed-type material racks must be spaced apart from each other to allow an aisle space for movement of the stacking machine during transport of the carrying boxes. When the number of the fixed-type material racks becomes large, the required number of aisle space is also correspondingly increased, thereby resulting in waste of space in the factory or warehouse. Further, the fixed-type material racks have poor stability problem, especially, because Taiwan is in a seismic zone, when earthquake comes, a single fixed-type material rack is prone to topple due to unstable center of gravity, resulting in accidental disaster for the personnel and products. Moreover, the flexibility of the fixed-type material racks is also not good. When a carrying box is stacked in a high place, the stacking machine must consume a longer transport time to move the carrying box to and fro the material rack, thereby resulting in inefficient transport.